Method of making tubes



Aug. 28, 1934. M. OSBORNE 1,971,829

' METHOD OF MAKING TUBES Q Filed June 18, 1931 2 Sheets-Sheet l INVENTVORY 1 Aug. 1934- M. M. OSBORNE 1,829

METHOD OF MAKING TUBES Filed June 18, 1931 2 Sheets-Sheet 2 INVENTOR V gm" Patented Aug. 28, 1934 UNITED STATES IlIETHOD OF MAKING TUBES Melvin M. Osborne, Youngstown, Ohio, assignor to The Youngstown Sheet and Tube Company, Youngstown, Ohio, a corporation of Ohio Application June 18, 1931, Serial No. 545,161

8 Claims.

The present invention relates broadly to the art of metal working, and more particularly to the production of so-called seamless tubes.

For many purposes, seamless tubes are preferred to welded tubes. The costs incident to the manufacture of seamless tubes, and particularly of certain sizes, together with the difliculties attendant upon the known processes of producing such tubes, and the lack of uniformity with respect to successive tubes has, however to a large extent at least, driven consumers to the use of welded tubes.

In accordance with known processes, seamless tubes are customarily produced either by the socalled Pilger process, the so-called American or automatic process, or the drawing process. Each of the processes referred to has certain advantages and objections. The drawing process is necessarily limited to tubes of smaller sizes and therefore has distinct limitations. The Pilger process is objectionable from the standpoint of crudity and lack of uniformity of the articles produced thereby. With the American or automatic process, there is produced a superior article with respect to quality and uniformity, together with a higher rate of production. In practicing this latter process, however, it is customary to pierce the billets to be utilized so that the wall diameter of the hollow billet is much thinner than the wall thickness for billets similarly pierced for use on a Pilger mill. Such a piercing operation is very severe with respect to its effect on the material of the billet, and not infrequently causes defects in the material which show up in the finishing operations incident to the tube manufacture.

The present invention contemplates a novel method and apparatus for the manufacture of seamless tubes in that it incorporates certain of the advantageous features of the Pilger mill together with the advantageous operating charac teristics of the American or automatic method.

In the accompanying drawings there is diagrammatically illustrated a system of apparatus effective forcarrying out the present invention. In the drawings:

Figure 1 is a diagrammatic plan view of a layout in accordance with the present invention;

Figure 2 is a detail sectional view, on an enlarged scale, of a so-called plug mill or high mill;

Figure 3 is a perspective view of a pierced billet such as fed to the Pilger mill;

Figure 4 is a longitudinal sectional view through a semi-finished article as produced in the Pilger mill; and

Figure 5 is a view similar to Figure 4 illustrating the product of the Pilger mill as divided intermediate its ends into a pair of blanks.

Having reference more particularly to Figure 1 of the drawings, there is illustrated a layout comprising a suitable number and arrangement of ingot heating furnaces 2 wherein the ingots or billets to be utilized are brought to the proper temperature. At this temperature they are carried in any well known manner to a piercing mill 3 wherein they are subjected to a piercing operation for the purpose of producing a hollow ingot or billet. 4 substantially as illustrated in perspective in Figure 3 of the drawings. This pierced billet is then delivered in any desired manner, as by a suitable conveyor 5, to a transfer track 6 cooperating at its ends with the rolls 7 of Pilger mills, which mills are adapted to be driven by a suitable mechanism 8 diagrammatically illustrated in the drawings. Cooperating with each of the Pilger mills, as. is customary in the art, are mandrel operating mechanisms and feeding mechanisms 9.

The product of the Pilger mill, which is in the form indicated generally in Figure 4, is passed by a suitable system of conveyors 10 to saws 11 where the crop end 12 is sawed off as indicated by the'line 14 (Figure 5), and the article sawed into one or more sections 15, two of which are indicated in Figure 5.

Each section 15 constitutes a semi-finished tube or pipe characterized by both a rough exterior and semi-finished interior, these qualities being characteristic of articles produced in a Pilger mill. Such semi-finished pipes are then conveyed by means of suitable transfer racks 16 and table 1'7 to a re-heating furnace 18 where they are again brought up to a forging temperature which is preferably in the neighborhood of 2100" F. Heated to this temperature, the semifinished pipes are delivered to and run through a plug mill or high mill 19.

Such a mill, as well understood in the art, and as illustrated in more or less detail in Figure 2, customarily comprises upper and lower rolls 20 and 21 respectively, having a suitable number of passes or grooves 22 formed therein and providing one or more passes, in each of which is located a plug or mandrel 23. In working the semifinished pipe, designated T in Figure 2, through the plug mill or high mill, the tube is put through the pass and returned through the same pass one or more times, until it is finished. This may be 7 sible with such a mill to produce tubing having a thinner wall than it is possible to produce on a Pilger mill. By utilizing the Pilger mill, however, as an initial forming means, it is unnecesor billet in the piercing sary to subject the ingot mill 3 to as severe a piercing operation as would be required if the billet were to be passed direct- 1y from the piercing mill to the high mill. It is thus always possible to maintain the piercing operation within such limits as not to strain or injure the material, and subsequently eff tial compensation in the Pilger mills. Inasmuch as the Pilger mill is utilized only as a semi-finishing step in the process, it is possible to speed up the Pilger mill operation, thus materially increasing its capacity, and bringing it morenearly into conformity with the capacity of the high mill. The high mill in turn is effective not only for removing the irregularities produced in the article by the severe working in the Pilger mill and thus smoothing both the inside and outside thereoflbut also for giving to the article the desired uniformity in wall thickness from end to end.

For purposes of a clearer understanding of the invention, five actual examples in accordance with the present invention will be referred to. In the following table, entitled Product desired, there appear in tabulated form five difierent pipe ect a paran accompanying reduction in the wall thickness averaging approxmately 1%. The plug mill was also effective for giving an increase in length of slightly less, on the average, than 30%.

Upon leaving the plug mill, the material had been subjected to three distinct working operations. These were respectively, the piercing operation, the Pilgering operation, and the rolling operation in the high mill. In each instance the article underwent a variation in dimensions both with respect to wall thickness and length, thus producing an article having a refined grain structure. In accordance with the present invention the refinement of the steel is further improved by delivering the product of the mill 19 to a suitable number of metal reelers 24, which in turn deliver by conveyors 25 to sizing mills (not shown).

As is well understood in the art, the operation of reeling a tube comprises passing the tube between short heavy rolls of special design usually so set in their housings as to lie side by side with their axes inclined a few degrees to the horizontal and in opposite directions, and with the rolls crossing each other at a corresponding angle exactly in the middle of their length. The rolls are customarily geared together to revolve in the same direction, and are motor driven at a fairly high rate of speed. Positioned in the pass SiZeSibetween the generally convex roll surfaces is a Product desired mandrel over which the tube must pass. Inas- Pipe size: much as the rolls are revolving in the same direc- 28# Gas. tlon, they cause rotation of both the tube and /8 H 36# Cas mandrel. Due to the inclination of the roll axes,

40# they are efiective for slowly drawing the tube T, 36# over the mandrel. Owing to the slow rate at T which the tubes are drawn through the rolls, the tubes are subjected to considerable working, and

In order to produce such articles, the Pilger leave the reeling machine practically straight, mill was set, adjusted and operated to give charperfectly round, of slightly enlarged diameter acteristic products as set forth in the following and with smooth burnished surfaces.

table: In the following table there appear the dimen From Pilger mill sions of the preceding articles, in the same order,

as delivered from the reeler:

No. of Sawed Z Wall pipes length From Tee er Length thickness iront each Wall thick- I o. D. I. D. M55 48' 0" 9.25" 8.45" .400 2 24' 0" so 0" 9.25" 8.244" .503 2 25 0" 50' o" 9. 625" 8.569 .528 2 25' 3" 8.392 48' 0" 10.25" 9.322" .404 2 24' 3" 9" 8.20" .400" 35' 9" 14. 375" 13.715" .330 1 3s 9" 9- 75 8. 5%" .425 9. 815" 9. 113" 351" 14. 375" 1a. 875 250" From the above table it will be noted that with the first four examples, the product of the Pilger mill was divided into two equal sections.

It will be noted that in each instance the outside and inside diameters have been increased, characteristic of the reeling machine, while retaining the same wall thicknesses.

Upon leaving the sizing mill, the respective The tabla articles had dimensions as indicated in the following table: Reduc- From szin mill Wall tion Reduc l E Elona g 0 D I D thickwall tion R01 ed longa' gation Hess thick thicklength tion W thick ness 2 Bess o. D. 1. D. Hess PET- I! II II Percent cent 3g 2% 8.5" 7.892" .304" .090" 24 32' 0" s 0" 33% 5 8.5" 7. 70" .40" .103" 20.41 32' 0" 7' 0" 28 9 31123" '3 s" 8.875" 8.025 .425" .103" 10.52 32' 0" 0' 0" 26.72 5 9.375" 8.675" .351" .113" 24.35 32' 0" 7' 9" 31.05 13. 315" 12.875" .250" .080 24.24 47' 0" 11"3" 31.41

' It will be noted that the sizing mill is effective From the above table it will be noted that in each instance both the outside and inside diameters of the tube were reduced, there being also for reducing the inside and outside diameters to the pipe size required in the finished product given in the first table, while retaining the same wall thicknesses as those characterizing the product of the plug mill and of the reeler.

The additional working performed in both the reeling and sizing units insures further refinement of the grain structure, thus giving a superior product. This product in addition to being characterized by a refined grain structure, is further characterized by a smoother inner and outer surface with a more even or uniform wall thickness than obtainable by a Pilger mill, together with complete elimination of the markings characteristic of the Pilger process. The tube sizes are likewise of greater accuracy and may have a thinner wall thickness than it is possible to produce on a straight Pilger mill or by a straight Pilger process. These features constitute certain advantages of the present invention.

'Further advantages arise from the greater production obtainable by reason of the fact that the Pilger mill may be operated at a greater speed since it is only called upon to produce a semifinished article, thus giving to the Pilger mill 2. capacity more nearly in accordance with the possible capacity of the high mill.

The finished articles are further characterized by a materially less variation in wall thickness in the finished tubes from end to end thereof than it is possible to obtain by any known modification of the Pilgering process.

While I have herein illustrated more or less diagrammatically certain preferred embodiments of the invention, it will be understood that changes in the characteristics of the units utilized, as well as in the steps to which the material is subjected, may be made without departing either from the spirit of the invention or the scope of my broader claims.

I claim:

1. In'the method of forming seamless tubes, the steps comprising piercing an ingot, reducing the wall thickness of the pierced ingot by a Pilgering process to produce a semi-finished tube, subjecting said tube to a sawing operation, reheating the tube, rolling the tube to smooth the surfaces thereof while decreasing the outside tube diameter and wall thickness, then reeling the tube, and thereafter sizing the reeled tube.

2. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a Pilgering process, operating the Pilger mill at a speed greater than the normal speed of operation of such a mill to produce a semi-finished tube, reheating the tube, passing the semi-finished tube through a plug mill to smooth the interior. and exterior surfaces while decreasing the outside diameter and wall thickness of the tube, then reeling and sizing the tube.

3. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a Pilgering process to produce a semi-finished tube, passing the semi-finished tube through a plug mill to smooth the interior and exterior surfaces while decreasing the outside diameter and wall thickness of the tube, and then reeling and sizing the tube.

4. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a Pilgering process to produce a semi-finished tube, passing the semi-finished tube at 'a relatively high temperature through a plug mill to smooth the interior and exterior surfaces while decreasing the outside diameter and wall thickness of the tube, and then reeling and-sizing the tube. 5. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a Pilgering process to produce a semi-finished tube, reheating the tube,- passing the semi-finished tube through a plug mill to smooth the interior and exterior surfaces while decreasing the outside diameter and wall thickness of the tube, and then sizing the tube.

6. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a Pilgering process to produce a semi-finished tube, smoothing the interior and exterior surfaces of the semi-finished tube while decreasing the .outside diameter and wall thickness of the tube, and thereafter increasing the tube. diameter while retaining the wall thickness, and then sizing the tube.

'7. In the method of forming seamless tubes, the steps comprising reducing the wall thickness of a hollow ingot by subjecting the same to a. Pilgering process to produce a semi-finished tube, smoothing the interior and exterior surfaces of the semi-finished tube while decreasing the outside diameter and wall thickness of the tube, thereafter increasing the tube diameter while retaining the wall thickness, and then sizing the tube by decreasing the diameter thereof while retaining substantially the same wall thickness. 8. In a method of finishing semi-finished tubes produced in a Pilger mill, the steps comprising reheating the semi-finished tube, then subjecting said tube while reheated to an operation for changing the outside diameter and decreasing the wall thickness thereof, smoothing the interior and exterior surfaces, and then sizing the tubes.

NIELVIN M. OSBORNE. 

